Project Summary/Abstract Innate lymphoid cells (ILCs) are recently identified constituents of innate immune system and have been the focus of intense investigation over the past five years. ILCs provide early immune protection against infectious agents, mediate lymphoid organogenesis and tissue repair, participate in the transition from innate to adaptive immunity, contribute to inflammation and autoimmunity, repair tissue damage and regulate metabolic homeostasis. My long-term goal is to establish a productive research group and ultimately to become a leading scientist in the area of ILCs, especially type 2 ILCs (ILC2s). My prior study has reported the existence of an inflammatory ILC2 (iILC2) population that is transient ILC progenitors mobilized by inflammation and infection; they are capable of developing into natural ILC2-like cells or ILC3-like cells and contributing to immunity to both helminthes and fungi (Huang et al., Nature Immunology 2015). The principle aim of this proposal is to elucidate the generation, migration and function of iILC2s. I will use multiple experimental technologies to identify the progenitors, understand the process of iILC2 trafficking and investigate iILC2 function in tissue repair and metabolic homeostasis. The initial phase of this project will be conducted in Laboratory of Immunology and Laboratory of System Biology NIAID, which provide a superb environment to fulfill my trainings and research. My mentor, Dr. Ronald Germain, is a world-leading immunologist. He is an NIH Distinguished Investigator and has published more than 300 scholarly research papers and reviews. He serves as an associate or advisory editor of the J Exp Med, Immunity, Current Biology, Mol Systems Biol, BMC Biology, Nature Communications, eLife, and Int Immunol, and has previously served as Deputy Editor of J Immunol and Editor, Immunity. He has received numerous awards and honors. He has trained dozens of postdoctoral fellows, many of whom now occupy senior academic posts and are internationally recognized investigators. I will take the advantage of NIH and Dr. Germain's laboratory to enhance my intellectual background of immunology, to expand my scope of scientific research, to learn necessary experimental technologies, and to improve my skills on grant writing mentoring, lab management and scientific communication. All these activities will secure my career transition from a postdoc fellow to an independent tenure-track faulty position.